The investigating team visited the factory yesterday where Abdul Hakim alias Hasan Sahib had been recruited about a fortnight before the blast on October 2, and collected samples of raw materials from the factory at Saraitikar village, in Santipara area, 1 km from the Khagragarh flat, where the blast occurred, NIA sources said.
Chemicals rich in aluminium and lead had been seized from the Khagragarh flat besides explosives after the blast and they would be matched with the samples collected from the wok (kadhai) factory, the sources said. The NIA team comprised four officers while the forensic team had three experts.
Sub-Inspector Akash Munshi of Bardhaman police station who was the first investigating officer probing the blast, also accompanied the team. The team members interrogated Sheikh Zakir Mir alias Sheikh Laltu, the owner of the wok factory where Hakim had been employed for a daily wage of Rs 100.
Hakim is now undergoing treatment for his injuries sustained in the blast at SSKM hospital in Kolkata. Mir revealed that Hakim who was then residing at Khagragarh, had told him that he was a resident of Mangalkot, near Simulia, 60 km from Burdwan town.
Zakir told investigators that Hakim had been brought to him by one Sheikh Asadullah, resident of Nazrulpally in Burdwan town, who was also in the wok business. Asadullah's daughter studied at Simulia madrasa which Hakim used to visit and was introduced to Asadullah by his daughter, NIA sources said.
The sources said Hakim could carry on his terror activities at the Khagragarh flat, a stone's throw away under the garb of a factory employee with access to the alloys used in woks for the purpose of making explosives.
The factory, employing ten workers which was closed for the Durga pujas before the October 2 blast, has remained shut since as the workers have left, the factory owner said.
On October 27, National Security Adviser Ajay Doval and NSG chief Jayanta Narayan Chowdhury interrogated Zakir, Asadullah and a couple of workers of the aluminium wok factory, the sources said.
NIA officials detained a suspect in connection with the blast and took him to Kolkata for interrogation yesterday, the sources added.